One who's Pubic Hair is a similar colour to that of the popular Coca-Cola Softdrink by the same name.
Often a "Fanta Pants" also has red/ginger hair, this is generally the result of a genetic disorder known as Gingavitas

The birth defect of a male born with striking orange hair that is seen growing wildly all over his body including great masses on his genitals.

When born with Fantapants the carrier is often very insecure and often turns into an abuser of alcohol and the English language as well as trying to find faults with his friends and falsely blow them out of proportion to try make his gross and pitiful state a little more conspicuous to the disgusted onlooker.